Related Experiment Video
Updated: May 31, 2026
11:56
Antimicrobial Peptides Produced by Selective Pressure Incorporation of Non-canonical Amino Acids
Published on: May 4, 2018
Natural Peptide antibiotics from tunicates: structures, functions and potential uses
Robert I Lehrer1, J Andrew Tincu, Steven W Taylor
1Department of Medicine.
Integrative and Comparative Biology
|June 18, 2011
Summary
Tunicates use innate immunity, with hemocytes producing antimicrobial peptides like styelins and clavanins. These peptides, especially modified Styelin D, show potent activity against bacteria, aiding host defense.
Area of Science:
- Marine biology
- Immunology
- Biochemistry
Background:
- Tunicates, like Styela clava, rely on innate immunity for host defense.
- Hemocytes are crucial for tunicate immunity, with S. clava possessing eight subtypes.
- Hemocyte extracts contain antimicrobial peptides.
Purpose of the Study:
- To identify and characterize antimicrobial peptides from Styela clava hemocytes.
- To investigate the structure, function, and localization of these peptides.
- To understand their role in host defense against bacterial pathogens.
Main Methods:
- Peptide isolation and purification
- cDNA cloning
- Histochemical staining for DOPA
- Immunocytochemistry
- Transmission and scanning electron microscopy
Main Results:
- Two families of antimicrobial peptides identified: styelins (phenylalanine-rich) and clavanins (histidine-rich).
- Styelin D exhibits extensive post-translational modifications, including 3,4-dihydroxyphenylalanine (DOPA) and 6-bromotryptophan, enhancing its bactericidal activity.
- Clavanins are effective at acidic pH and found in granulocytes and macrophages.
- Styelin D and clavaspirin induce osmotic dysregulation in bacteria, leading to cell death.
Conclusions:
- Styela clava hemocytes produce a diverse arsenal of antimicrobial peptides, styelins and clavanins, crucial for innate immunity.
- Post-translational modifications significantly enhance peptide antimicrobial activity.
- These peptides represent an effective host defense mechanism against bacterial infections.
Related Concept Videos
01:23Antimicrobial Proteins
Antimicrobial proteins are important components of the immune system. They aid the body in combating pathogens by either killing them directly or hindering their replication processes. Four main types of antimicrobial substances are interferons, the complement system, iron-binding proteins, and antimicrobial proteins.
Interferons
Interferons (IFNs) are proteins produced by lymphocytes, macrophages, and fibroblasts infected with viruses. While IFNs cannot prevent viruses from entering and...
Interferons
Interferons (IFNs) are proteins produced by lymphocytes, macrophages, and fibroblasts infected with viruses. While IFNs cannot prevent viruses from entering and...
01:28Peptidoglycan Synthesis
Structure of PeptidoglycanPeptidoglycan is a vital structural component of the bacterial cell wall, providing mechanical strength and shape to the cell. It consists of repeating units of two sugars—N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)—linked by β-1,4 glycosidic bonds. These sugar chains are cross-linked by short peptide chains, forming a mesh-like polymer that surrounds the bacterial plasma membrane.Cytoplasmic Phase – Precursor SynthesisPeptidoglycan biosynthesis begins in...
01:23Inhibitors of Gram-positive Cell Wall Synthesis
Bacterial cell walls are typically rigid structures composed mainly of peptidoglycan, a mesh-like polymer that provides mechanical strength and maintains cell shape. The synthesis of peptidoglycan is a crucial process in bacterial growth and serves as a primary target for many antibiotics.Mechanism of Action of Beta-Lactam AntibioticsBeta-lactam antibiotics, such as penicillin, inhibit peptidoglycan synthesis in actively growing cells. These antibiotics share a characteristic four-membered...
01:56Structural Protein Function
Structural proteins are a category of proteins responsible for functions ranging from cell shape and movement to providing support to major structures such as bones, cartilage, hair, and muscles. This group includes proteins such as collagen, actin, myosin, and keratin.
Collagen, the most abundant protein in mammals, is found throughout the body. In connective tissue, such as skin, ligaments, and tendons, it provides tensile strength and elasticity. In bones and teeth, it mineralizes to form...
Collagen, the most abundant protein in mammals, is found throughout the body. In connective tissue, such as skin, ligaments, and tendons, it provides tensile strength and elasticity. In bones and teeth, it mineralizes to form...
01:27Production of Antibiotics
Penicillin, one of the earliest and most widely used antibiotics, is produced industrially by the filamentous fungus Penicillium chrysogenum. Large stirred-tank bioreactors ranging from tens to hundreds of thousands of liters maintain tightly controlled temperature, pH, and dissolved oxygen conditions to support fungal metabolism and maximize antibiotic yield. Penicillin is a secondary metabolite, synthesized primarily during the stationary growth phase, which requires a carefully managed...
01:28Gene Regulation in Microbial Communities: Quorum Sensing
Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...